US 12,282,003 B1
Method for calibrating sound velocity applied to multi-layer variable thickness structure
Zhichao Fan, Hefei (CN); Jingwei Cheng, Hefei (CN); Xiangting Xu, Hefei (CN); and Yangguang Bu, Hefei (CN)
Assigned to HEFEI GENERAL MACHINERY RESEARCH INSTITUTE CO., LTD., Hefei (CN)
Filed by HEFEI GENERAL MACHINERY RESEARCH INSTITUTE CO., LTD., Anhui (CN)
Filed on Nov. 18, 2024, as Appl. No. 18/951,585.
Application 18/951,585 is a continuation of application No. PCT/CN2024/091372, filed on May 7, 2024.
Claims priority of application No. 202311765200.1 (CN), filed on Dec. 21, 2023.
Int. Cl. G01N 29/30 (2006.01); G01N 29/07 (2006.01)
CPC G01N 29/30 (2013.01) [G01N 29/07 (2013.01); G01N 2291/011 (2013.01); G01N 2291/0231 (2013.01); G01N 2291/106 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A method for calibrating a sound velocity applied to a multi-layer variable thickness structure, comprising:
S1, constructing a planar multi-layer medium stacked structure and determining a sound velocity of each layer of medium material in the planar multi-layer medium stacked structure;
S2, establishing a curved multi-layer medium stacked structure, the curved multi-layer medium stacked structure being arranged with a plurality of discrete elements; establishing a fluctuation equation for determining a sound pressure value of each of the plurality of discrete elements;
S3, establishing a loss function between the sound pressure value and a measured sound pressure value of the plurality of discrete elements; and
S4, performing a gradient descent calculation on the sound pressure value based on the loss function, iteratively updating to obtain a sound velocity value until a minimum value of the loss function is obtained, wherein the sound velocity value is as a weighting parameter in the plurality of discrete elements, and the sound velocity value is an optimal speed value;
wherein S1 further includes:
S11, constructing the planar multi-layer medium stacked structure, selecting n types of medium materials, the medium materials being arranged in stacked layers sequentially from top to bottom along a vertical direction, and a contact surface between two adjacent layers of medium materials constituting a horizontal reflective plane;
S12, irradiating the planar multi-layer medium stacked structure by using an ultrasound emitter with array elements arranged sequentially and equidistantly along a straight line, the irradiation process including:
S121, selecting a planar multilayer medium stacked structure in a cuboid shape, establishing a space rectangular coordinate system O-XYZ by designating a thickness direction of the planar multi-layer medium stacked structure, i.e., a direction in which the plurality of medium materials are arranged in stacked layers sequentially from the top to bottom along the vertical direction, as a positive direction of a Z-axis, designating a width direction of the planar multi-layer medium stacked structure as a positive direction of a Y-axis, and designating a length direction of the planar multi-layer medium stacked structure as a positive direction of an X-axis; wherein a top surface of the planar multi-layer medium stacked structure coincides with an XY surface, and a corner of the top surface coincides with a coordinate origin O;
S122, arranging the array elements on the ultrasound emitter sequentially and equidistantly along a straight line; moving the ultrasound emitter along a positive direction of the Y-axis to vertically irradiate the reflective plane and form a moving trajectory, and an arrangement direction of the array elements being parallel to the positive direction of the X-axis during the movement of the ultrasound emitter;
S123, repeatedly moving the ultrasound emitter along the positive direction of the Y-axis multiple times to form a moving trajectory corresponding to each of a plurality of lanes, the plurality of lanes being parallel to each other along the position direction of the Y-axis, and a distance between adjacent moving trajectories being equal to a distance between adjacent array elements;
wherein a sound velocity of an ultrasonic wave emitted by the ultrasound emitter propagation in a kth layer of medium material is ck, and a thickness of the kth layer of medium material is dk, and based on the sound velocity of the ultrasonic wave and the thickness of medium material, a corresponding time is calculated based on a time calculation equation, the time calculation equation is:

OG Complex Work Unit Math
wherein ti,j,k denotes a time taken for the ultrasonic wave emitted by an ith array element to propagate to the kth layer of medium material and to be received by a jth array element after being reflected in a reflective plane of the kth layer of medium material; ti,j,k denotes a time taken for the ultrasonic wave emitted by the ith array element to propagate to the kth layer of medium material and to be received by the ith array element after being reflected in the reflective plane of the kth layer of medium material; custom character denotes a root-mean-square of a sound velocity from a first layer of medium material to the kth layer of medium material; xi,r denotes a positional coordinate of the ith array element in a rth moving trajectory on the X-axis; xj,r denotes a positional coordinate of the jth array element in the rth moving trajectory on the X-axis;
S13, calculating custom character based on ck with the following equation:

OG Complex Work Unit Math
wherein tk denotes a single-trip time of vertical propagation of the ultrasound wave in the kth layer of medium material; cn denotes a root-mean-square of a sound velocity from the first layer of medium material to an nth layer of the medium material; ti,j,k−1 denotes a time taken for the ultrasonic wave emitted by the ith array element to propagate to a k−1th layer of medium material and to be received by the ith array element after being reflected in the reflective plane of the kth layer of medium material;
S14, a n−1th layer of medium material satisfying a following equation:

OG Complex Work Unit Math
wherein custom character denotes a root-mean-square of a sound velocity from the first layer of medium material to the n−1th layer of medium material; and
S15, obtaining a sound velocity expression equation of cn by the equation in S13 and the equation in S14, wherein the sound velocity expression equation is:

OG Complex Work Unit Math
wherein ti,i,n−1 denotes a time used for the ultrasonic wave emitted by the ith array element to propagate to the n−1th layer of medium material and to be received by the ith array element after being reflected in a reflective plane of the n−1th layer of medium material; ti,i,n denotes a time used for the ultrasonic wave emitted by the ith array element to propagate to a nth layer of medium material and to be received by the ith array element after being reflected in a reflective plane of the nth layer of the medium material;
wherein values of custom character, ti,i,n, custom character, ti,i,n−1, ti,i,k, and ti,i,k−1 are measured by corresponding measuring instruments, and by substituting the values into the specific expression equation of cn, a sound velocity of the ultrasonic wave propagating in the medium material is obtained.