阅读说明：本技术 一种避免产生弯曲应力的双轴预应力施加装置 (Double-shaft prestress applying device capable of avoiding bending stress ) 是由 彭光健 陈建锋 徐风雷 窦贵靖 赵城城 张泰华 于 2019-09-26 设计创作，主要内容包括：一种避免产生弯曲应力的双轴预应力施加装置,包括基座、滑轨、滑块、应力施加组件、载荷传感器、活动夹具、压片及紧固螺栓,基座为L型,基座上设置有带槽的凸台用于放置试样；载荷传感器一端与活动夹具连接,另一端与应力施加组件连接,并配备有相应的载荷显示器；活动夹具通过螺纹与载荷传感器连接,上端加工出矩形凹槽,与十字型试样端部的矩形接头配合；压片通过紧固螺栓与基座连接；基座上固定有滑轨,连接块及活动夹具与滑块配合；十字型试样两端安装在基座上,另外两端安装在活动夹具上。本发明施加拉、压应力的方式简单、方便,不产生额外的弯曲应力,且无需频繁更换应力施加组件,提高了工作效率。(A biaxial prestress applying device for avoiding bending stress comprises a base, a slide rail, a slide block, a stress applying assembly, a load sensor, a movable clamp, a pressing sheet and a fastening bolt, wherein the base is L-shaped and is provided with a boss with a groove for placing a sample; one end of the load sensor is connected with the movable clamp, the other end of the load sensor is connected with the stress applying assembly, and the load sensor is provided with a corresponding load display; the movable clamp is connected with the load sensor through threads, and a rectangular groove is machined at the upper end of the movable clamp and matched with a rectangular joint at the end part of the cross-shaped sample; the pressing sheet is connected with the base through a fastening bolt; a sliding rail is fixed on the base, and the connecting block and the movable clamp are matched with the sliding block; two ends of the cross-shaped sample are arranged on the base, and the other two ends of the cross-shaped sample are arranged on the movable clamp. The invention has simple and convenient method for applying the tensile stress and the compressive stress, does not generate additional bending stress, does not need to frequently replace the stress applying component and improves the working efficiency.)

1. A biaxial prestress applying device capable of avoiding bending stress is characterized by comprising a base, a slide rail, a slide block, a stress applying assembly, a load sensor, a movable clamp, a pressing sheet and a fastening bolt, wherein the base is L-shaped, and a boss with a groove is arranged on the base and used for placing a sample;

one end of the load sensor is connected with the movable clamp, the other end of the load sensor is connected with the stress applying assembly, and the load sensor is provided with a corresponding load display;

the movable clamp is connected with the load sensor through threads, a rectangular groove is processed at the upper end of the movable clamp, and the movable clamp is matched with a rectangular joint at the end part of the cross-shaped test sample and used for applying tensile and compressive stress to the test sample;

the pressing sheet is connected with the base through a fastening bolt and is used for pressing the cross-shaped sample;

a sliding rail is fixed on the base, the connecting block and the movable clamp are matched with the sliding block, and the connecting block and the movable clamp move on the sliding rail to transfer tensile and compressive stress;

two ends of the cross-shaped sample are arranged on the base, and the other two ends of the cross-shaped sample are arranged on the movable clamp.

2. The device for applying double-shaft prestress capable of avoiding generating bending stress as claimed in claim 1, wherein the stress applying assembly comprises a driving motor, a coupler, a lead screw and a connecting block, the connecting block is provided with a threaded through hole in the center, the left end of the connecting block is connected with the lead screw, the right end of the connecting block is connected with the load sensor, the lead screw is driven to rotate by the driving motor, the connecting block is further driven to move in the lead screw, and the generated tension or pressure acts on the sample through the load sensor and the movable clamp.

3. The biaxial prestress applying device for avoiding the generation of bending stress as set forth in claim 1 or 2, wherein the tension and compression load applied by the stress applying assembly is positioned at the intersection of the horizontal center plane and the vertical symmetry plane of the cross-shaped test piece.

4. The biaxial pre-stress applying apparatus for avoiding generation of bending stress as set forth in claim 1 or 2, wherein the amount of deformation of the specimen when the stress applying member applies tensile stress is smaller than the width of the reserved gap.

Technical Field

The invention relates to the field of material mechanics testing devices, in particular to a biaxial prestress applying device capable of avoiding bending stress.

Background

The existence of residual stress can influence the processing precision and the size precision of a service workpiece, so that the workpiece deforms. The presence of residual stresses accelerates brittle cracking of the part, thereby reducing the fatigue strength of the part, affecting the life of the workpiece. The method can accurately test the magnitude and direction of the residual stress in the part, and has important influence on the engineering field. At present, a nondestructive residual stress detection method, namely an instrumented indentation method, is widely researched, and in order to calibrate the residual stress detection method, the magnitude and the direction of the residual stress in a sample must be known. It is often necessary to pre-stress the sample with the aid of a residual stress introducing device to simulate the residual stress.

The existing residual stress applying device mainly generates stress through two modes of bending and tension and compression, the residual stress introduced by a method for bending a sample is unevenly distributed on the surface of the sample, the stress size needs to be obtained through calculation, and the error is large. The method can generate uniform residual stress in the sample by utilizing a tension-compression method, and when the conventional biaxial tension-compression stress applying device applies stress to the cross sample, the center position of the sample is deviated under the action of the tension force due to the fact that the freedom degree of the cross sample is completely limited, so that bending stress is introduced to one side of the cross sample, and the test result is finally influenced. Therefore, it is necessary to design a device capable of applying biaxial tension and compression stress to the sample without introducing other interference stress, so as to improve the accuracy of residual stress detection.

Disclosure of Invention

In order to overcome the defects that the existing one-dimensional tension and compression residual stress applying device cannot introduce more complex plane residual stress and the two-dimensional tension and compression residual stress applying device easily introduces bending stress into a sample so as to influence a test result, the invention provides the double-shaft prestress applying device for avoiding generating the bending stress.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a biaxial prestress applying device capable of avoiding bending stress comprises a base, a slide rail, a slide block, a stress applying assembly, a load sensor, a movable clamp, a pressing sheet and a fastening bolt, wherein the base is L-shaped, and a boss with a groove is arranged on the base and used for placing a sample;

the stress applying assembly comprises a driving motor, a coupler, a lead screw and a connecting block, a threaded through hole is formed in the center of the connecting block, the left end of the connecting block is connected with the lead screw, the right end of the connecting block is connected with a load sensor, the lead screw is driven to rotate through the driving motor, the connecting block is further driven to move in the lead screw, and generated tensile force or pressure acts on a sample through the load sensor and a movable clamp;

one end of the load sensor is connected with the movable clamp, the other end of the load sensor is connected with the stress applying assembly, and the load sensor is provided with a corresponding load display;

the movable clamp is connected with the load sensor through threads, a rectangular groove is processed at the upper end of the movable clamp, and the movable clamp is matched with a rectangular joint at the end part of the cross-shaped test sample and used for applying tensile and compressive stress to the test sample;

the pressing sheet is connected with the base through a fastening bolt and is used for pressing the cross-shaped sample;

a sliding rail is fixed on the base, the connecting block and the movable clamp are matched with the sliding block, and the connecting block and the movable clamp move on the sliding rail to transfer tensile and compressive stress;

two ends of the cross-shaped sample are arranged on the base, and the other two ends of the cross-shaped sample are arranged on the movable clamp.

Furthermore, the stress applying assembly comprises a driving motor, a coupler, a lead screw and a connecting block, a threaded through hole is formed in the center of the connecting block, the left end of the connecting block is connected with the lead screw, the right end of the connecting block is connected with a load sensor, the lead screw is driven to rotate through the driving motor, the connecting block is further driven to move in the lead screw, and generated tensile force or pressure acts on the sample through the load sensor and the movable clamp;

still further, the tensile and compressive load applied by the stress applying assembly is positioned at the intersection of the horizontal central plane and the vertical symmetrical plane of the cross-shaped test sample.

Furthermore, the deformation amount of the sample when the stress applying component applies the tensile stress is smaller than the width of the reserved gap.

The invention has the following beneficial effects: the device can generate the residual stress of any tension-compression combination in a plane, and ensures that the cross-shaped sample is under the action of the residual stress of the double shafts; the device can ensure that the stress state of the central test area of the cross-shaped sample is uniform and stable, and other interference stress such as bending stress is not introduced except tensile stress and compressive stress; the device has the advantages that the device has dual purposes of tension and compression, two test loading conditions of tension stress and compression stress can be realized on the cross-shaped sample through the stress applying assembly only by controlling the steering of the motor, and the operation is simple; the device is integrally designed, the structure is simple, the residual stress introduced into the cross-shaped sample is directly measured by the load sensor, and the device is accurate and reliable; the base of the device is provided with a guide rail for the movement of the connecting block and the movable clamp, so that the direction of the applied force in the loading process is strictly parallel to the guide rail, and the device is stable and accurate; this device has pressed fixed preforming on the sample, plays the effect that compresses tightly to the sample, prevents that the sample from taking place warp deformation, reduces the clearance between sample and the base, guarantees measurement accuracy.

Drawings

FIG. 1 is a schematic view of the entire apparatus of the present invention

FIG. 2 is a top view of the apparatus of the present invention

FIG. 3 is a single block diagram of the apparatus of the present invention

FIG. 4 is a cross-shaped test area schematic view of a sample

The device comprises a base 1, a sliding block 2, a sliding rail 3, a motor support 4, a driving motor 5, a coupler 6, a screw rod 7, a connecting block 8, a load sensor 9, a movable clamp 10, a cross-shaped test sample 11, a pressing sheet 12, a test area 13 and a fastening bolt 14.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Referring to fig. 1 to 4, a biaxial prestress applying device for preventing bending stress from being generated includes a base 1, a stress applying assembly, a load sensor 9, a movable clamp 10, and a pressing plate 12. The base 1 is designed into an L shape, a boss with a cross-shaped groove is arranged in the middle of the base and used for placing a sample 11 to be tested, and bosses are arranged on two sides and used for fixing the motor support 4 and the driving motor 5.

The stress applying assembly comprises a driving motor 5, a coupler 6, a lead screw 7 and a connecting block 8, wherein the connecting block is fixed with the sliding block 2 and moves on the sliding rail 3 under the driving of the lead screw 7. One end of the stress applying component is fixed with the base 1, and the other end of the stress applying component is connected with the load sensor 9 through threads and used for applying tensile stress or compressive stress to the cross-shaped test sample 11.

The load cell 9 is a commercial mature product and the applied load size is directly readable from a mating load display.

The bottom of the movable clamp 10 is connected with the sliding block 2 and can move on the sliding rail 3, the top of the movable clamp is used for clamping a cross-shaped test sample 11, and the side surface of the movable clamp is connected with the load sensor 9 through threads and matched with the load sensor for transmitting tensile stress or compressive stress introduced by the stress applying assembly.

When stress is applied, the stress applying assembly rotates by controlling the driving motor 5, so that the screw rod 7 is driven to rotate, the connecting block 8 is further driven to move on the sliding rail 3, so that tensile stress or compressive stress is generated, and the tensile stress or the compressive stress acts on the cross-shaped test sample 11 through the load sensor 9 and the movable clamp 10.

The four ends of the cross-shaped test specimen 11 are designed as rectangular interfaces and cooperate with rectangular recesses on the movable clamp 10, both for tension and compression.

The use method of the invention comprises the following steps: referring to fig. 1, firstly, a cross-shaped sample 11 to be measured is placed on a boss of a base 1, a rectangular joint at the end part of the sample is clamped on a movable clamp 10, then a pressing sheet 12 is placed on the cross-shaped sample 11, and the pressing sheet 12 is tightly pressed and fixed on the base 1 by a fastening bolt 14 and is used for tightly pressing the cross-shaped sample 11, so that the sample is prevented from warping and deforming, and the gap between the sample 11 and the base 1 is reduced. After the sample is installed, the tensile stress control switch of the driving motor 5 is turned on, the sample is pulled in the X-axis direction, the compressive stress control switch of the driving motor 5 is turned on in the same way, the sample is pressed in the Y-axis direction, and the applied stress can be read through a matched display.

After the applied tensile stress or compressive stress value is stable, the device is placed on instrumented press-in equipment for experiment, after the required data are measured, the driving motor is controlled to enable the stress applying assembly to apply other stress values, and the experiment process is repeated.

After the experiment is finished, the residual stress of the cross-shaped sample is calculated according to relevant experimental data and by combining the studied residual stress test method, and the test result is compared with the applied stress true value for analysis, so that the accuracy of the residual stress test method is verified.

The two-dimensional stress applying device without bending interference stress can generate uniformly distributed stress on the surface of the area to be measured of the sample by simultaneously applying force on the two symmetrical sides of the sample. The device has simple structure, stable stress state and convenient application process of tensile stress and compressive stress, and can be used as a standard stress applying device for testing the residual stress on the surface of a material.

The foregoing is considered as illustrative only of the preferred embodiments of the invention, and the scope of the invention is not to be construed as limited to the particular forms set forth, but is intended to be limited only to the modifications and variations provided they do not depart from the spirit and scope of the invention.