Material testing machine and gripping force detecting method

Patent metadata

Field	Value
Publication number	US-10928281-B2
Application number	US-201816166185-A
Country	US
Kind code	B2
Filing date	Oct 22, 2018
Priority date	Nov 22, 2017
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

Provided are a material testing machine and a gripping force detecting method that can easily judge whether a test piece is gripped with an appropriate gripping force by a gripper. A controlling section is connected to a FFT transforming section via a load cell; the FFT transforming section calculates a natural frequency of a system comprising a test piece and an upper gripper which is connected to a load cell based on a detected value of a force of the load cell. In addition, the controlling section is connected to a storing section which stores the natural frequency calculated by the FFT transforming section. Furthermore, the controlling section is also connected to a comparing section which compares the natural frequency calculated by the FFT transforming section and the natural frequency stored by the storing section before a test starts.

First claim

What is claimed is:

1. A material testing machine, which conducts a tensile test by applying a tensile test force to a test piece in a state when both ends of the test piece are gripped by a pair of grippers, comprising:
a memory, which stores an appropriate natural frequency, wherein a natural frequency of a system comprising the test piece and one of the pair of grippers when the test piece is gripped with an appropriate gripping force by the one gripper is the appropriate natural frequency;
a before-test natural frequency measuring means, which measures a before-test natural frequency, wherein a natural frequency of the system comprising the test piece and the one gripper when the test piece is gripped by the one gripper before the tensile test starts is the before-test natural frequency;
a comparing section, which compares the before-test natural frequency with the appropriate natural frequency; and
a controlling section, which allows the starting of a material test when the before-test natural frequency is greater than the appropriate natural frequency, and conducts a warning display when the before-test natural frequency is smaller than the appropriate natural frequency.

2. A material testing machine, which conducts a tensile test by applying a tensile test force to a test piece in a state when both ends of the test piece are gripped by a pair of grippers, and by measuring the tensile test force with a force detector which is connected to one of the pair of grippers, comprising:
a calculating section, which calculates a natural frequency of a system comprising the test piece and the gripper connected to the force detector, based on a detected value of a force of the force detector when the gripper connected to the force detector is batted;
a memory, which stores an appropriate natural frequency, wherein a natural frequency, calculated by the calculating section, of the system comprising the test piece and the gripper connected to the force detector when the gripper connected to the force detector is batted in a state when the test piece is gripped with an appropriate gripping force by the gripper connected to the force detector is the appropriate natural frequency;
a comparing section, which compares a before-test natural frequency with the appropriate natural frequency which is stored in the memory, wherein a natural frequency, calculated by the calculating section, of the system comprising the test piece and the gripper connected to the force detector when the gripper connected to the force detector is batted in a state when the test piece is gripped by the gripper connected to the force detector before the tensile test starts is the before-test natural frequency; and
a controlling section which allows the starting of a material test when the before-test natural frequency is greater than the appropriate natural frequency, and conducts a warning display when the before-test natural frequency is smaller than the appropriate natural frequency.

3. A gripping force detecting method, which detects whether a test piece is gripped with an appropriate gripping force by a pair of grippers in a material testing machine, which conducts a tensile test by applying a tensile test force to the test piece in the state when both ends of the test piece are gripped by the grippers, the gripping force detecting method comprising:
an appropriate natural frequency storing process of storing an appropriate natural frequency, wherein a natural frequency of a system comprising the test piece and one of the pair of grippers when the test piece is gripped with an appropriate gripping force by the one gripper is the appropriate natural frequency;
a before-test natural frequency measuring process of measuring a before-test natural frequency, wherein a natural frequency of the system comprising the test piece and the one gripper when the test piece is gripped by the one gripper before the tensile test starts is the before-test natural frequency;
a comparing process of comparing the before-test natural frequency with the appropriate natural frequency;
a step of allowing the starting of a material test when the before-test natural frequency is greater than the appropriate natural frequency; and
a step of conducting a warning display when the before-test natural frequency is smaller than the appropriate natural frequency.

4. A gripping force detecting method which detects whether a test piece is gripped with an appropriate gripping force by a pair of grippers in a material testing machine, which conducts a tensile test by applying a tensile test force to the test piece in a state when both ends of a test piece are gripped by the pair of grippers, and by measuring the tensile test force with a force detector which is connected to one of the pair of grippers, the gripping force detecting method comprising:
a first measuring process of measuring a detected value of the force of the force detector when the gripper connected to the force detector is batted in a state when the test piece is gripped with an appropriate gripping force by the gripper connected to the force detector;
an appropriate natural frequency calculating process of calculating an appropriate natural frequency based on the detected value of the force of the force detector which is measured in the first measuring process, wherein a natural frequency of a system comprising the test piece and the gripper connected to the force detector is the appropriate natural frequency;
a second measuring process of measuring a detected value of the force of the force detector when the gripper connected to the force detector is batted in a state when the test piece is gripped by the gripper connected to the force detector before the tensile test starts;
a before-test natural frequency calculating process of calculating a before-test natural frequency based on the detected value of the force of the force detector which is measured in the second measuring process, wherein a natural frequency the system comprising the test piece and the gripper connected to the force detector is the before-test natural frequency;
a comparing process of comparing the before-test natural frequency with the appropriate natural frequency; and
a step of allowing the starting of a material test when the before-test natural frequency is greater than the appropriate natural frequency; and
a step of conducting a warning display when the before-test natural frequency is smaller than the appropriate natural frequency.

Assignees

• Shimadzu Corp

Inventors

• Iwakiri Shogoro
• Miyazaki Zen

Classifications

• G01N3/08 Primary

  by applying steady tensile or compressive forces (G01N3/28 takes precedence) · CPC title

• G01N3/22

  by applying steady torsional forces (G01N3/26, G01N3/28 take precedence) · CPC title

• G01N3/066

  with electrical indicating or recording means · CPC title

• G01N3/30

  by applying a single impulsive force, e.g. by falling weight · CPC title

• G01N29/12

  by measuring frequency or resonance of acoustic waves {(measuring frequency or resonant frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04, G01H13/00; acoustic resonators G10K11/04; vibration or shock testing of structures G01M7/00)} · CPC title