DE900023C - Torsion testing machine, on which the test specimen is simultaneously subjected to torsion and bending stress - Google Patents

Description

Torsion testing machine, on which the test specimen is simultaneously subjected to a and is subjected to bending stress For testing materials and machine parts, that are to be stressed in terms of twisting and bending, it is for manufacturing equivalent test conditions are often necessary, both of the test specimen at the same time Subject to types of stress.

For this purpose, special machines have been proposed in which the composite stress due to synchronization by means of electrical control is effected. Such machines are complex, fragile and expensive. To They become in longer use as a result of abrasion and erosion of the synchronization contacts inaccurate.

The invention relates to a simple, adjustable device on a conventional torsion testing machine, with the help of which a test object (test rod or machine part) any desired combination of twisting and bending is imposed can be.

Devices for torsion testing machines for producing bends are known per se. They consist of cranks that are clamped into the torsion heads will. The test rod is in a plane perpendicular to the torsion axis on the two Crank pin attached. Fig. I shows such a device in the scheme. I and 2 are the torsion heads; 3 and 4 the two flanged cranks, the are rotated against each other in the torsion axis o-o. A test rod 5 is between the crank pins 3 'and 4' clamped so that its axisV-V with the torsion axiso-o forms an angle a = go °. When twisted, the test rod will only bend claimed. Combined torsion stress is not possible here.

In contrast, the invention is based on the idea that a between the torsion heads clamped rod whose torsion axis coincides with the torsion axis the torsion testing machine cuts at an acute angle, at the same time Torsion and bending is stressed. The invention therefore contemplates tension members on both torsion heads, in which the test specimen is fastened in this way can be.

This results in the following simple ones for full or hollow rod specimens Relationship for determining the cutting angle: Mb - sina a M, z cos a = tang a, where Mb is the bending moment and Md is the torque stressed by the specimen and a means the angle of intersection of the two torsion axes.

For solid and hollow rod specimens, this relationship assumes that the intersection of the two torsion axes is in the middle of the bar. In the case of differently shaped specimens, the virtual center of torsion must be the point of intersection found empirically or mathematically; d. H. the point where no torsion takes place when the rod is twisted at the same angle at both ends.

To adapt the intersection to different given experimental conditions to be able to, the invention provides clamping members, which the setting on a Allow preselected angle amount.

For this purpose, according to the invention, clamping members which are in circular guide tracks are suitable are displaceable and an adjustment of the test specimen to the cutting angle with inevitable Allow the torsion axis intersection point to be held in the center of the test specimen.

The circular guide can have a prismatic profile and an angular scale be provided while the pointer is mounted on the clamping member.

Reliable around the two guide cutouts when clamping the test object to bring to a common level and the center of the test object on the intersection of the two torsion levels, inserts are provided through which the cutouts the latter must be completed in full.

Since with every torsion a shortening and bending at the same time a shortening of the chord of the test specimen takes place, would be more rigid with completely Arrangement of the whole restraint tensile loads occur and the measurement results be falsified. To avoid such tensile stresses it is provided that one of the bearings of the torsion testing machine or one of the clamping members is longitudinally displaceable is arranged.

The schematic Fig. 2 illustrates an adjustable device according to the invention. To the two torsion heads 6 and 7 one (not shown) Two clamping members 8 and 9 are flanged on the torsion testing machine. You insist each from a slot-like circular arc guide 8 'and 9' and one guide stone each 8 "and 9". In the guide stones 8 "and 9", the test piece 10 is attached so that its center Z with the intersection of the machine axis TT and the torsion axis does the examinee coincides. The angle a enclosed by the two axes TT and TT, results from the above-mentioned relationship between the two moments with which the test object should be charged.

If the torque MD of the testing machine is initiated, then MS = b or Mb = MD. sin a sin α and analogously Md = MD cosa therefore as above Mb ~ sina = tang α.

Md - cos a thong.

Claims (4)

PATENT CLAIMS: I. Torsion testing machine on which the test object is simultaneously subjected to torsion and bending stress, characterized by clamping members on the two torsion heads of the torsion testing machine, in which a test specimen can be fastened at two points so that its torsion axis intersects the torsion axis of the torsion testing machine at an acute angle. 2. torsion testing machine according to claim I, characterized by Tensioning members that adjust the angle of intersection between the torsion axes allow the test specimen and the torsion testing machine to a preselected angular amount. 3. torsion testing machine according to claim 2, characterized in that that the clamping members can be displaced in sections of a guideway, which an adjustment of the test specimen to the cutting angle with inevitable retention of the torsion axis intersection in the middle of the test object. 4. Twist testing machine according to claim 3, characterized by inserts for the guideways through which the sections of the latter are completely fill out. Cited publications: German patent specification No. 677 436.