Chengdu Miniature Mechanical Testing Science & Technology Co. Ltd. (MMTI) is a high-tech enterprise jointly developing and applying material nano-testing technologies in collaboration with the research team from Southwest Jiaotong University. The indentation mechanical testing and analysis systems—MMTI-S (In-service Indenter), MMTI-R (Micro-sample Indenter), MMTI-SR (All-round Indenter), MMTI-SR-XYA (Bi-directional Automatic Indentation System), and the MMTI-C Component Tester—are small, portable devices developed based on C Theory (Energy Density Equivalence Theory). Under nano-scale, approximately homogeneous and isotropic material conditions, and based on the energy density equivalence of the Representative Volume Element (RVE) in continuum mechanics, these systems enable indentation loading on the surfaces of micro-samples or component materials using spherical, conical, and planar indenters, as well as composite indenters (cone-cone, plane-cone, and cone-plane). They also apply uniaxial tensile or compressive loading to small-sized component specimens (e.g., rings, disks, spheres, SPT disks) and cracked specimens (e.g., CT, SEB). By measuring load-displacement curves, the systems achieve the characterization of macroscopic material deformation behavior and the acquisition of fundamental mechanical laws and performance indices. The testing methods and instrument products based on C Theory overcome the immense difficulties faced by traditional testing methods in accurately testing the macroscopic elastic-plastic mechanical laws of structural service materials, welded joints, and small-sized advanced materials in critical engineering projects (such as petrochemical, nuclear power, aviation, high-speed rail, special equipment, etc.) under different environments. They can measure the material's fundamental mechanical laws: stress-strain relationships, and fundamental mechanical properties: Elastic Modulus, Yield Strength, Tensile Strength, Uniform Elongation, Brinell (4 scales), Rockwell (3 scales), Vickers (1 scale), and Knoop Hardness (1 scale), totaling 14 indicators. particularly for welded joints, the systems can accurately measure residual stress through a composite indentation test at a single point while simultaneously determining a series of mechanical property indicators including mechanical laws.

Through the MMTI-SR-XYA Bi-directional Automatic Indentation System, the equipment possesses the capability to automatically complete continuous indentation on at least 10 measurement points along a linear direction on the tested surface, with point spacing precisely settable within the range of 0.5mm to 2mm, and an indentation range of 10mm to 20mm. This automated function significantly improves testing efficiency, making it particularly suitable for array indentation on welded joints and high-throughput testing demands for large batches of samples. This function is applicable to the precision indentation testing of tiny laboratory samples and is fully compatible with on-site inspection applications for in-service structures. Furthermore, for materials prepared in advanced manufacturing fields such as additive manufacturing, this function allows for the rapid and systematic characterization of the spatial distribution of mechanical properties, providing an efficient and reliable evaluation method for new material development and process optimization.

Through the MMTI-C Component Tester, in addition to measuring the aforementioned indicators on a series of micro-samples, material fracture toughness can be measured using cracked specimens (e.g., CT, SEB). Through funnel-shaped small specimens, the material's low-cycle fatigue Manson-Coffin law can be measured, and the material's fatigue crack propagation Paris law can be further obtained through low-cycle energy density equivalence conversion.

The company's chief scientist team has achieved analytical solutions for a series of elastic-plastic problems, including elastic-plastic indentation. They proposed and invented a series of advanced material testing methods based on conical, cylindrical-planar, and cone-cylinder composite indenter indentation tests, as well as small punch tests, ring tests, and fracture toughness tests. Collectively, they have published over 70 high-level papers (33 JCR Q1 papers) and obtained over 20 authorized invention patents, including 5 national invention patents authorized to MMTI and 1 software copyright. Based on the theory and testing methods of metal material indentation, the company's chief scientist presided over the formulation of the National Standard GB/T 37782-2019 with independent Chinese intellectual property rights: "Metallic materials—Determination of strength, hardness and stress-strain relationship by indentation" (Chinese and English versions), GB/T 46428.1-2025 "Metallic materials—Plate and rod micro-specimens—Part 1: Fatigue testing method," and the China Group Standard T/CSTM 00287-2021: "Standard Test Method for Compressive Testing of Metallic Rings to Determine Strength and Stress-Strain Relationship."